The present invention relates to a magnetic disc apparatus, and in particular to a magnetic disc apparatus comprising a magnetic head for writing and reading data to and from a magnetic disc, a slider for floating up the magnetic head from the magnetic disc, a suspension for supporting the slider, and an IC chip connected on the suspension, and as well to a servo-track slider for writing servo-tracks on a magnetic disc.
These years, as to magnetic disc apparatuses, the demand for increasing the recording capacity and miniaturizing the size while speeding up the reading and the writing have become higher and higher, and accordingly, there have been attempted the technological development for increasing the recording density and the transfer speed. One of problems in the high speed transmission technology is a signal transmission to and from a magnetic head.
Heretofore, an IC for processing signals from a magnetic head is mounted in a part (a carriage section in general) after the position where wirings from a plurality of magnetic heads are integrated. In order to speed up the transmission of signals, it is required to shorten the rise-up time or the fall-down time of pulse signals transmitted from the magnetic head. However, since the wiring for transmitting signals has a parasitic capacity and an inductance component inherent thereto, there has been raised such a problem that the time delay is caused as to steep rise-up or fall-down of signals. Further, since this problem relates to the length of wiring, it is clear, the longer the wiring, the greater the disadvantage.
In view of the above-mentioned situation, as to the wiring length between the position where the IC is mounted, and the magnetic head, the parasitic capacitance and the inductance components inherent to the wiring are not negligible, and accordingly, there have been found limits. Thus, it has been tried to mount, for respective magnetic heads, required parts of a control circuit of the IC, including a signal amplifying part used as a preamplifier, at a position which is near to each of magnetic heads so that the wiring length from the magnetic head becomes shorter (these IC will be hereinbelow referred to xe2x80x9chead ICsxe2x80x9d).
As to the mounting position, it is mounted on a suspension as disclosed in JP-A-11-195215.
Heat generation from the above-mentioned head IC has been already known as one of the problems which would occur in the case of mounting the head IC on the suspension. In order to lower the high temperature of the IC caused by the heat generation, the JP-A-11-195215 proposes the mounting position of the head IC which is on the suspension and which is at a surface faced to a magnetic disc.
Specifically, due to the heat generation from the head IC, as a countermeasure for deformation of the suspension or the head arm, the head IC is mounted in a part which is center in both in-plan direction and thickenesswise direction of the head arm, as disclosed in JP-A-2000-113610.
By the way, throughout experiments carried out by the applicants, it has been found a problem in which an averaged seek time becomes longer in a magnetic disc apparatus incorporated with a head IC than in a magnetic disc apparatus incorporated with no head IC. No such a point is shown or suggested from the above-mentioned prior art examples.
An object of the present invention is to restrain the averaged seek time from becoming longer. The positioning of a magnetic head is carried out by changing over, in accordance with a condition in which the magnetic head is positioned, the operation among three kinds of modes, that is, a mode in which a magnetic head is moved at a high speed to a position around its desired position in accordance with positional information on a magnetic disc, that is, the so-called track information, a mode in which the magnetic head is finely adjusted to the desired position and a tracking mode in which the magnetic head is caused to follow the desired position, and the seek time is a time elapsing from the time when the magnetic head is to move the desired position to the time when the operation is shifted into the tracking mode.
It has been clearly found from the results of experiments and studies made by the applicants that the above-mentioned problem is caused by a rate of variation in temperature difference between the inner side and the outer side of the head IC, caused by heat which is generated from the IC head and which raises the temperature of the suspension around the head IC.
More specifically, it has been found that a displacement of the head part at the tip end of the suspension is caused as the temperature difference between both sides of the suspension on which the IC chip is mounted, is increased upon writing of servo-tracks (servo pattern), and accordingly, the servo-pattern cannot be settled to equal pitches until the above-mentioned temperature difference becomes constant. Further, should the positioning of the head is carried out for reading operation or writing operation in accordance with the servo-pattern with unequal pitches, vibration during the positioning of the head becomes larger, and accordingly, the positioning speed is lowered, resulting a longer seek time.
Further, it has been found that the temperature difference between both sides of the suspension become constant when only three seconds elapses from the time of starting the writing of the servo-track (servo-pattern), and thereafter, the pitches of servo-pattern become equal to one another.
To the end, according to the present invention, there is provided a magnetic disc apparatus comprising a magnetic head for writing or reading data to and from a magnetic disc, a slider for floating up the magnetic head from the magnetic disc on rotation, a suspension for supporting the slider, a positioning mechanism for positioning the magnetic head to a predetermined radial position, and an IC chip mounted on the suspension, wherein a rate of variation in temperature difference between opposite sides of a position where the IC chip is mounted, on an IC mounting surface of the suspension is set to be less than 3.5 k per sec.
Further, the rate of variation in temperature difference is preferably set to.be less than 1.4 K per sec. Moreover, the magnetic disc apparatus is caused to carry out spurious writing operation until the rate of variation in temperature difference becomes less than 3.5 K per sec. Further the magnetic disc apparatus is caused to carry out spurious writing operation until the rate of variation in temperature difference becomes preferably less than 1.4 K.
Further, the spurious wiring operation is carried out by at least three seconds in a part other than data tracks on a magnetic disc. Further, the above-mentioned IC chip is a signal amplifier for writing and reading data with the use of a magnetic head. Further, the above-mentioned spurious writing operation causes the above-mentioned IC chip to write data which is invalid for the apparatus, on the magnetic disc. Further, the above-mentioned rate of variation in temperature difference is that from the time of starting of writing of a servo-pattern.
Further, there is provided a magnetic disc apparatus comprising a magnetic head for writing or reading data to and from a magnetic disc, a slider for floating up the magnetic head from the magnetic disc on rotation, a suspension for supporting the slider, a positioning mechanism for positioning the magnetic head to a predetermined radial position, and an IC chip mounted on the suspension, wherein spurious writing operation is carried out by a time longer than at least 3 sec in a part other than data tracks on the magnetic disc during the operation of writing a servo-pattern.
Further, the above-mentioned spurious writing operation causes the IC chip to write data invalid for the apparatus, on the magnetic disc.
Further, the rate of an area of signal lines on a surface underneath the position where the IC chip is mounted, is set to be larger on the inner peripheral side of the magnetic disc than on the outer peripheral side thereof, when it is compared between both sides of the IC chip as a center on the surface. Further, signal lines arranged in a part underneath the IC chip are formed at least by the underneath surface of the IC chip in its entirety, or signal lines having an area larger than the area of the IC chip, and the signal lines are formed so as to be led toward the inner peripheral side of the magnetic disc.
Further, the signal lines are formed so as to be led toward one side of the suspension, remote from the magnetic head. Further, the signal lines underneath the suspension are formed of dummy copper wiring, and power supply lines for the IC chip is arranged on the inner peripheral side of the magnetic disc.
Further, holes are formed in the suspension, and the area of each of the holes on the outer peripheral side of the magnetic disc is smaller than that on the inner peripheral side thereof while the number of the holes on the outer peripheral side of the disc is greater than that on the inner peripheral side thereof so that the total of the areas of the holes on the outer peripheral side of the magnetic disc is equal to that on the inner peripheral side thereof.
According to the present invention, as stated above, by taking the effect of the heat generation from the IC chip during the drive of the magnetic disc into consideration, servo-tracks can be written at substantially equal pitches. As a result, it is possible to restrain the seek time from becoming longer.